Insulation for SOFC Systems

ABSTRACT

The invention is directed to insulating compositions for use in solid oxide fuel cells. Such compositions can be used to prevent seal damage and increase the electrical and ion efficiency.

CLAIM FOR PRIORITY

This application claims priority to U.S. Provisional Application No.60/958,409, filed Jul. 5, 2007, which is incorporated by this referencein its entirely.

FIELD OF THE INVENTION

The present invention relates to insulation for solid oxide fuel cell(SOFC) systems.

TECHNICAL BACKGROUND

SOFC systems typically produce DC electrical power by reacting fuelswith oxygen from air in single cells. Multiple DC cells are electricallyconnected in series or parallel, usually in series to increase voltage.For SOCF's using H₂ as a fuel and oxygen from the air as an oxidizer,each cell can produce about 1.1-1.2 volts at open circuit and mayproduce power at between 1.1-0.5 volts per cell at temperatures of 400°C.-1,000° C. When multiple cells are connected in series, substantialvoltages can occur.

One SOFC design features multiple cells on a single sheet ofelectrolyte. At least one sheet and usually two electrolyte sheets aresealed to a frame where the fuel flows between the electrolyte sheet(s)and inside the frame. The combination of at least one sheet (usually twoelectrolyte sheets with multiple cells) and frame is known as a packet.A substantial voltage difference appears between different areas on theelectrolyte and between the electrolyte and a conducting (sometimesgrounded) packet frame. This voltage, for example up to ˜+/−18 voltsopen circuit for sixteen cells connected in series on one electrolytesheet, can electrochemically degrade and destroy glass seals wherechemical components of the seal move under electric field at theoperating temperature of the SOFC system. The sign, magnitude, andlocation of the voltage between the seal and the frame in a multiplecell electrolyte design depends upon whether the frame is grounded,ungrounded (“floats”), or if the frame is connected to a particular celland particular electrode to determine (“pin”) the potential of theframe.

As discovered herein in the present invention, plasma sprayed alumina(PSA) coatings on metal solid oxide fuel cell components can havemechanical failure in the PSA layer. CTE mismatch and microstructure ordefects in the microstructure of the PSA coating may play a significantrole in the fracture of the coating. The magnesium aluminate spinel plusmagnesia coatings can react detrimentally with some glass seals.

As discovered herein in the present invention, in addition to sealdegradation and power loss/efficiency losses, stray parasitic electricalor ionic currents in SOFC systems can cause other degradation materialreactions, particularly in multi-cell designs on a single electrolytesheet. In such multi-cell systems, a voltage of about 2.2-2.4 volts canexist across the gap between the cells (called a via gallery), betweenthe anode on one cell and the un-connected cathode of an adjacent cellof less than 1 mm distance. Stray/parasitic oxygen ion or electroniccurrent can flow across this 1 mm or less gap, reducing the power outputof the device, and this current may cause material/structure degradationby a variety of mechanisms.

As discovered herein in the present invention, there are also efficiencylosses associated with the “short-circuit” regions near the viaelectrical interconnects. For certain SOFC designs, which have multiplecells electrically interconnected through a continuous electrolytesupport, the presence of an electronically conductive element whichtraverses from the cathode side to the anode side—i.e. the“via-fill”—surrounded by ionically conductive electrolyte support (i.e.3YSZ), produces a small electrical short, a parasitic current, local tothe via.

There is a need to address the aforementioned problems and othershortcomings of SOFCs, especially those containing multiple cellsconnected in series. These needs and other needs are satisfied by theinsulation technology of the present invention.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to the use of insulation inparticular locations of the SOFC. In another aspect, the presentinvention utilizes particular insulation compositions. The presentinvention addresses at least a portion or all of the problems describedabove through the use of either the insulation location or composition.The compositions can be used for components and parts of components,such as layers on conducting frames, insulating frames, layers andinsulating regions in or on the electrolyte. These insulatingcompositions prevent, minimize, or reduce electrochemical sealdegradation, power loss, and/or stray/parasitic electrical and ionicreactions in SOFC systems.

In a first detailed aspect, the present invention provides a solid oxidefuel cell comprising a cathode, an anode, an electrolyte, a bus bar, avia pad, a seal, and an insulating amount of an insulating composition,wherein the insulating composition is proximate to the bus bar and/orthe via pad and/or is present in part of the electrolyte, wherein theinsulating composition is not substantially disposed between the cathodeand the electrolyte.

In a second detailed aspect, the present invention provides a solidoxide fuel cell comprising a cathode, an anode, an electrolyte, a busbar, a via pad, a seal, and an insulating amount of an insulatingcomposition, wherein the insulating composition is proximate to the busbar and/or the via pad and/or is present in part of the electrolyte,wherein the insulating composition is not lanthanum zirconate orstrontium zirconate.

In another detailed aspect, the present invention n provides a solidoxide fuel cell comprising a cathode, an anode, an electrolyte, a busbar, a via pad, a seal, and an insulating amount of an insulatingcomposition comprising one or more insulating oxide ceramics having thefollowing crystal structure class, super class, derivative structure orsuperstructure of the following crystal structure type:

-   -   i) pyrochlore or distorted pyrochlore,    -   ii) perovskite, distorted perovskite, superstructure of        perovskite, or interleaved perovskite-like structure,    -   iii) fluorite, distorted fluorite, fluorite like, anion        defective fluorite, sheelite, fergusonite, or flourite related        ABO₄ compound,    -   iv) spinel, spinel derived structure, or inverse spinel,    -   v) rock salt structure,    -   vi) ilmenite,    -   vii) pseudobrookite A₂BO₅,    -   viii) stoichiometric structure based on ReO₃-like blocks,    -   ix) bronze or tetragonal bronze structure based on ReO₃-like        blocks,    -   x) rutile;    -   xi) trirutile crystal structure or columbite crystal structure        of AB₂O₆,    -   xii) cubic rare earth (C-M₂O₃) structure, or    -   xiii) corundum, or    -   a mixture thereof or a solid solution thereof,    -   wherein the insulating composition is proximate to the bus bar        and/or the via pad    -   and/or is present in part of the electrolyte.

In another detailed aspect, the present invention provides a solid oxidefuel cell comprising a cathode, an anode, an electrolyte, a bus bar, avia pad, a frame, a seal, and an insulating amount of an insulatingcomposition comprising one or more insulating oxide ceramics having thefollowing crystal structure class, super class, derivative structure orsuperstructure of the following crystal structure types:

-   -   i) pyrochlore or distorted pyrochlore,    -   ii) perovskite, distorted perovskite, superstructure of        perovskite, or interleaved perovskite-like structure,    -   iii) fluorite, distorted fluorite, fluorite like, anion        defective fluorite, sheelite, fergusonite, or a flourite related        ABO₄ compound,    -   iv) ilmenite,    -   v) pseudobrookite A₂BO₅,    -   vi) stoichiometric structure based on ReO₃-like blocks,    -   vii) bronze or tetragonal bronze structure based on ReO₃-like        blocks,    -   viii) rutile,    -   ix) trirutile crystal structure or columbite crystal structure        of AB₂O₆, or    -   x) cubic rare earth (C-M₂O₃) structure, or    -   a mixture thereof or a solid solution thereof,    -   wherein the insulating composition is proximate to the frame of        the solid oxide fuel cell.

In another detailed aspect, the present invention provides a fuel cellsystem comprising at least two solid oxide fuel cells of the invention.

Additional aspects and advantages of the invention will be set forth, inpart, in the detailed description, figures, and any claims which follow,and in part will be derived from the detailed description or can belearned by practice of the invention. The advantages described belowwill be realized and attained by means of the elements and combinationsparticularly pointed out in the appended claims. It is to be understoodthat both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the invention as disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several aspects described below.Like numbers represent the same elements throughout the figures.

FIG. 1 shows the thermal expansion coefficient of various pyrochlores(rare earth zirconates) and zirconia 8 mole % yttria (YSZ).

FIG. 2 shows electrical resistivity as a function of temperature forrare earth stanates and zirconates (pyrochlore structures) measured inan atmosphere of 1 bar of oxygen or 10⁻³ bar of oxygen.

FIG. 3 shows the electrical resistivity as a function of +3 to +5 cationratio at 600° C. for distorted fluorite structures,ZrO₂—Y(RETH)Nb(Ta)O₄—Y(RETH)₂O₃.

FIG. 4 shows the thermal expansion coefficient of ZrO₂˜25 mole %YTaO₄˜0.5 mole % Ta₂O₅.

FIG. 5 shows an approximate phase diagram in the ZrO₂ rich corner of theZrO₂—YNb(Ta)O₄—Y(RETH)O_(3/2) system at 1300-1600 C.

FIG. 6 shows an X-ray diffraction trace of Example 1, identifying alayer of a tetragonal crystal structure (distorted fluorite) ofzirconia-yttrium tantalate on a tetragonal zirconia electrolyte with aminor amount of NiO.

FIGS. 7 a and b show a SEM cross-section that is 7 a (polished) or 7 b(fractured) of Example 1, which is a layer of a tetragonal crystalstructure (distorted fluorite) of zirconia-yttrium tantalate on atetragonal zirconia electrolyte.

FIG. 8 a shows an X-ray diffraction trace of Example 2, identifying alayer of a pyrochlore structure of Nd₂Zr₂O₇ on a tetragonal zirconiaelectrolyte.

FIG. 8 b shows an SEM cross-section of fractured tetragonal zirconiaelectrolyte with a Nd₂Zr₂O₇ pyrochlore layer and with a thin dense layerof a reaction product as produced in Example 2.

FIG. 9 a shows a top view of a pictorial representation of anelectrolyte supported multiple-cell design of one aspect of theinvention.

FIG. 9 b shows a side view of a multiple-cell design along cut line A-A.

FIG. 9 c is an exploded view of the metal filled via current path of oneaspect of the invention.

FIG. 9 d is an exploded view of the electrolyte sheet showing the viaholes of one aspect of the invention.

FIG. 10 shows a schematic view of a multiple-cell design of one aspectof the invention along cut line A-A of FIG. 9 a.

FIG. 11 is a schematic side view of a multiple-cell design of one aspectof the invention along cut line B-B of FIG. 9 a.

FIG. 12 a is a schematic showing bus bars, via pads and electrodes for amulti-cell design on a single electrolyte of one aspect of theinvention.

FIG. 12 b is a schematic showing regions/areas or volumes where theinventive insulating ceramics can be used on or in the electrolyte witha multi-cell design of one aspect of the invention.

FIG. 13 shows a schematic of an electrolyte with an insulating coatingor volume/region underneath the bus bars and via galleries of amulti-cell device of one aspect of the invention.

FIG. 14 is a pictorial 3D representation of a packet of one aspect ofthe invention.

FIGS. 15 a and 15 b show a top-level view and a side level view of aschematic of an electrolyte with an insulating volume/region surroundingthe active area and extending to make contact with the seal of oneaspect of the invention.

FIGS. 16 a and 16 b are a top level view and a side level view of aschematic of an electrolyte with an insulating volume/region surroundingthe active area but not making contact with the seal of one aspect ofthe invention.

FIG. 17 is a schematic diagram of the inventive insulating ceramic beingused as a coating between a frame and a seal in an SOFC system of oneaspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be understood more readily by reference to thefollowing detailed description, examples, and claims, and their previousand following description. However, before the present compositions,articles, devices, and methods are disclosed and described, it is to beunderstood that this invention is not limited to the specificcompositions, articles, devices, and methods disclosed unless otherwisespecified, as such can, of course, vary. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular aspects only and is not intended to be limiting.

The following description of the invention is provided as an enablingteaching of the invention in its currently known embodiments. To thisend, those skilled in the relevant art will recognize and appreciatethat many changes can be made to the various aspects of the inventiondescribed herein, while still obtaining the beneficial results of thepresent invention. It will also be apparent that some of the desiredbenefits of the present invention can be obtained by selecting some ofthe features of the present invention without utilizing other features.Accordingly, those who work in the art will recognize that manymodifications and adaptations to the present invention are possible andcan even be desirable in certain circumstances and are a part of thepresent invention. Thus, the following description is provided asillustrative of the principles of the present invention and not inlimitation thereof.

Disclosed are materials, compounds, compositions, and components thatcan be used for, can be used in conjunction with, can be used inpreparation for, or are products of the disclosed method andcompositions. These and other materials are disclosed herein, and it isunderstood that when combinations, subsets, interactions, groups, etc.of these materials are disclosed that while specific reference of eachvarious individual and collective combinations and permutation of thesecompounds may not be explicitly disclosed, each is specificallycontemplated and described herein. Thus, if a class of substituents A,B, and C are disclosed as well as a class of substituents D, E, and Fand an example of a combination embodiment, A-D is disclosed, then eachis individually and collectively contemplated. Thus, in this example,each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F arespecifically contemplated and should be considered disclosed fromdisclosure of A, B, and C; D, E, and F; and the example combination A-D.Likewise, any subset or combination of these is also specificallycontemplated and disclosed. Thus, for example, the sub-group of A-E,B-F, and C-E are specifically contemplated and should be considereddisclosed from disclosure of A, B, and C; D, E, and F; and the examplecombination A-D. This concept applies to all aspects of this disclosureincluding, but not limited to any components of the compositions andsteps in methods of making and using the disclosed compositions. Thus,if there are a variety of additional steps that can be performed it isunderstood that each of these additional steps can be performed with anyspecific embodiment or combination of embodiments of the disclosedmethods, and that each such combination is specifically contemplated andshould be considered disclosed.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings:

As used herein, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to a “compound” includes aspects having two or moresuch compounds, unless the context clearly indicates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not. For example, the phrase “optionally substituted component”means that the component can or can not be substituted and that thedescription includes both unsubstituted and substituted aspects of theinvention.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another aspect includes from the one particular value and/orto the other particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint.

As used herein, a “wt. %” or “weight percent” or “percent by weight” ofa component, unless specifically stated to the contrary, refers to theratio of the weight of the component to the total weight of thecomposition in which the component is included, expressed as apercentage.

As used herein, a “mole percent” or “mole %” of a component, unlessspecifically stated to the contrary, refers to the ratio of the numberof moles of the component to the total number of moles of thecomposition in which the component is included, expressed as apercentage.

Re is rhenium.

RETH is defined herein to be a rare earth element (also known as alanthanide), which includes herein Y and Sc.

As briefly introduced above, the present invention provides for a SOFCdevice that has an insulating material either in a particular locationor of a particular composition. This invention overcomes the heretoforeunknown and/or unrecognized problems with thin film alumina. Theinsulating compositions of this invention have low electronic and ionconductivity, as well as having thermal expansion coefficients nearlymatched (or at least better matched than alumina) to the zirconiaelectrolyte or frame. The materials of this invention can also besintered onto or reacted with the electrolyte to form an electronicallyand ionically insulating layer or region.

The insulating composition of the present invention is not intended tobe in contact with the cathode. However, due to inadvertent overlap fromthe printing process, some insulation may contact the cathode, either ontop of or underneath the cathode. The present invention, by the use ofthe term “not substantially disposed between the cathode and theelectrolyte,” is intended to include this inadvertent overlap with thecathode. In various such aspects, at least 50 wt. %, at least 60 wt. %,at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, at least 95 wt.%, at least 98 wt. % or at least 99 wt. % of the insulating compositionproximate the bus bar and/or the via pad is not disposed between thecathode and the electrolyte.

In one aspect, the insulating composition is not lanthanum zirconate orstrontium zirconate. In another aspect, the insulating composition isnot a rare earth zirconate or an alkaline earth zirconate. In yetanother aspect, the insulating composition comprises one or moreinsulating oxide ceramics. In one aspect, the insulating compositionshave a melting point of at least 700° C.

In one aspect, the insulating composition comprises one or moreinsulating oxide ceramics having the following crystal structure class,super class, derivative structure or superstructure of the followingcrystal structure type:

-   -   i) pyrochlore or distorted pyrochlore,    -   ii) perovskite, distorted perovskite, superstructure of        perovskite, or interleaved perovskite-like structure,    -   iii) fluorite, distorted fluorite, fluorite like, anion        defective fluorite, sheelite, fergusonite, or flourite related        ABO₄ compound,    -   iv) spinel, spinel derived structure, or inverse spinel,    -   v) rock salt structure,    -   vi) ilmenite,    -   vii) pseudobrookite A₂BO₅,    -   viii) stoichiometric structure based on ReO₃-like blocks, for        example ReO₃, TiNb₂O₇, or Ti₂Nb₁₀O₂₉,    -   ix) bronze or tetragonal bronze structure based on ReO₃-like        blocks,    -   x) rutile;    -   xi) trirutile crystal structure or columbite crystal structure        of AB₂O₆,    -   xii) cubic rare earth (C-M₂O₃) structure, or    -   xiii) corundum, or    -   a mixture thereof or a solid solution thereof.

In a further aspect of the above, the insulating oxide ceramic comprisesone or more of

-   -   i) pyrochlore or distorted pyrochlore crystal structure        according to the formula        -   (1) A₂B₂O₇ having the valence A³⁺ ₂B⁴⁺ ₂O₇, wherein            -   A³⁺ is Sc, Y, La, Nd, Eu, Gd, or other 3+ lanthanide and            -   B⁴⁺ is Zr, Ti, Hf, or Sn, or        -   (2) A₂B₂O₇ having the valence A²⁺ ₂B⁵⁺ ₂O₇, wherein            -   A²⁺ is Ca, Sr, Zn, or Ba,            -   B⁵⁺ is Nb, Ta, or V;    -   ii) perovskite; distorted perovskite crystal structure;        superstructure of Perovskite according to the formula ABO₃        -   (1) having the valence A²⁺B⁴⁺O₃, wherein            -   A²⁺ is Mg, Ca, Sr, or Ba and            -   B⁴⁺ is Ti, Zr, Hf, or Sn, for example CaTiO₃,        -   (2) having the valence A³⁺B³⁺O₃, wherein            -   A³⁺ is Sc, Y, La, or a 3+ lanthanide and            -   B³⁺ is Al, Ga, Cr, Sc, V, or Y,            -   for example, the rhombohedral perovskite LaAlO₃, or        -   (3) having the valence A²⁺(B³⁺ _(0.5)B⁵⁺ _(0.5))O₃, wherein            -   A²⁺ is Ca, Sr, or Ba,            -   B³⁺ is Al, Cr, Ga, Sc, Y, La, Ce, or other 3+                lanthanide,            -   B⁵⁺ is V, Nb, Ta, or Sb,            -   for example, Ca(La_(0.5),Ta_(0.5))O₃,        -   (4) having the valence A²⁺(B²⁺ _(0.33)B⁵⁺ _(0.67))O₃,            wherein            -   A²⁺ is Ca, Sr, or Ba,            -   B²⁺ is Mg, Ca, Cd, Ni, or Zn,            -   B⁵⁺ is Nb, Ta, or Sb,            -   for example, Ba(Ca_(0.33), Nb_(0.67))O₃ or Ba(Sr_(0.33),                Ta_(0.67))O₃,        -   (5) having the valence A²⁺(B²⁺ _(0.5)B⁶⁺ _(0.5))O₃, wherein            -   A²⁺ is Ca, Sr, or Ba,            -   B²⁺ is Mg, Ca, Sr, Ba, Cd, Ni, or Zn,            -   B⁶⁺ is Mo, W or Re,            -   for example, Ba(Sr_(0.5)W_(0.5))^(O) ₃,        -   (6) having the valence A³⁺ _(0.33)B⁵⁺O₃, wherein            -   A³⁺ is Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, or Er,            -   B⁵⁺ is Nb or Ta,            -   for example, La_(0.33)TaO₃, or        -   (7) having the valence A³⁺(B²⁺ _(0.5)B⁴⁺ _(0.5))O₃, where            A³⁺ is La or a lanthanide,            -   B²⁺ is Mg, and B⁴⁺ is Ti, for example,                La(Mg_(0.5),Ti_(0.5))O₃ or            -   Nd(Mg_(0.5),Ti_(0.5))O₃;        -   interleaved Bi₂O₂, for example, Bi₃NbTiO₉, Bi₄Ti₃O₁₂ or            BaBi₄Ti₄O₁₅; or a perovskite-like structure,    -   iii)        -   (1) fluorite or distorted fluorite of            A_(1−x−y)B_(x)C_(y)O_(−z), where A is Zr, Hf, or Ce, B is            Mg, Ca, Y, Sc, or a rare earth, C is V, Nb, or Ta, where            x<1, y<1, x+y<1, and z depends upon the valence of B and C,            wherein, if B is 2+, then z=2+0.5y−x, and if B is 3+, then            z=2+0.5y−0.5x,        -   (2) fluorite like compound of A_(1−x−y)B_(x)C_(y)O_(z),            where A is Zr, Hf, or Ce, B is Mg or Ca, and C is W or Mo,            where x<1, y<1, x+y<1, and z is 2+y−x,        -   (3) a sheelite type structure of ABO₄, where A is Mg or Ca            and B is W or Mo,        -   (4) a fergusonite type structure of M^(III)NbO₄, M^(III)TaO₄            or M^(III)VO₄, where M^(III) is a metal of valence +3, or            formula ABO₄ where A is Y or a rare earth and B is Nb, Ta or            V,        -   (5) an anion defective fluorite, or        -   (6) a flourite related ABO₄ compound, with valence A²⁺B⁶⁺O₄            or A³⁺B⁵⁺O₃,            -   wherein A²⁺ is Ca or Ba, B⁶⁺ is Cr, A³⁺ is Cr, and B⁵⁺                is Nb,    -   iv)        -   (1) a spinel structure or a spinel derived structure of            AB₂O₄, where A is Mg, Ni, Zn, Co, Fe, or Mn and B is Al, Ga,            Cr, or Fe,        -   (2) A₃B₃₂O₅₁, where A is Ca, Ba or Sr and B is Al,        -   (3) an inverse spinel or A₂BO₄, wherein A is Mg or Zn and B            is Ti or Sn,    -   v) rock salt structure AO, where A is Mg, Ca, Sr, Ba, or Ni,    -   vi) ilmenite of formula ABO₃, wherein A is Ni, Co, Mn or Fe and        B is Ti, for example FeTiO₃, or giekielite where A is Mg and B        is Ti, for example MgTiO₃,    -   vii) pseudobrookite crystal structure of the formula A₂BO₅,        wherein A is Al or Fe and B is Ti, for example Al₂TiO₅,    -   viii) a tetragonal bronze structure based on ReO₃-like blocks,        for example stoichiometric bronzes ReO₃, TiNb₂O₇ or Ti₂Nb₁₀O₂₉,        or a Nb₂O₅—WO₃ mixture, for example WNb₂O₈ or Nb₁₂WO₆₃,    -   ix) a tetragonal bronze of valence A²⁺B⁵⁺ ₂O₆, wherein A²⁺ is Sr        or Ba and B⁵⁺ is Nb or Ta, for example BaNb₂O₆ and SrNb₂O₆; or        the superstructure A²⁺ ₅B⁵⁺ ₁₀O₃₀, A²⁺ ₆B⁴⁺ ₂B⁵⁺ ₈O₃₀, for        example Ba₆Ti₂Nb₈O₃₀, Ca₂Sr₄Ti₂Nb₈O₃₀ or Ba₆Ti₂Ta₈O₃₀, or A²⁺        ₅B³⁺B⁴⁺ ₃B⁵⁺ ₇O₃₀, for example Sr₅LaTi₃Nb₇O₃₀, where A²⁺ is Ca,        Sr, or Ba, B³⁺ is La or a lanthanide, B⁴⁺ is Ti, and B⁵⁺ is Nb        or Ta,    -   x) rutile structure of AO₂, wherein A is Ti, Sn, or Mn,    -   xi) a trirutile crystal structure of AB₂O₆, for example MgTa₂O₆,        Cr₂WO₆, MgSb₂O₆, or VTa₂O₆, where A is Mg, Cr, or V and B is Ta,        W, or Sb; or other chain structure with trirutile stoichiometry,        such as for example, CaTa₂O₆,    -   xii) a cubic rare earth (C-M₂O₃) structure A₂O₃, where A is Y or        a rare earth, or    -   xiii) a corundum structure A₂O₃, where A is Al, Ga, or Cr, or        ABO₃, wherein A is Ni and B is Cr,    -   or a mixture thereof or a solid solution thereof.

In yet a further aspect of the above, the insulating oxide ceramiccomprises one or more of

-   -   i) Pyrochlore or distorted pyrochlore crystal structure of        La₂Zr₂O₇, Y₂Zr₂O₇, Nd₂Zr₂O₇, Gd₂Zr₂O₇, Er₂Zr₂O₇, La₂Hf₂O₇,        Y₂Hf₂O₇, Nd₂Hf₂O₇, Gd₂Hf₂O₇, Er₂Hf₂O₇, La₂Sn₂O₇, Y₂Sn₂O₇,        Nd₂Sn₂O₇, Gd₂Sn₂O₇, or Er₂Sn₂O₇,    -   ii) perovskite, distorted perovskite crystal structure,        superstructure of perovskite, or interleaved perovskite-like        structure of SrZrO₃, BaZrO₃, SrHfO₃, BaHfO₃, SrSnO₃, BaSnO₃,        BaTiO₃, or SrTiO₃,    -   iii) fluorite; distorted fluorite of A_(1−x−y)B_(x)C_(y)O_(z),        where A is Zr, Hf, or Ce and B is Mg, Ca, Y, Sc, or a rare earth        and C is V, Nb, or Ta where x<1, y<1 and x+y<1 and y/x>0.5, and        z depends upon the valence of B and C, wherein, if B is 2+, then        z=2+0.5y−x, and if B is 3+, then z=2+0.5y−0.5x; fluorite like        compound of A_(1−x−y)B_(x)C_(y)O_(z), where A is Zr, Hf, or Ce,        B is Mg or Ca and C is W or Mo, where x<1, y<1 and x+y<1 and        y/x>0.5, and z is 2+y−x; sheelite type structure of ABO₄, where        A is Mg or Ca, B is W or Mo; fergusonite type structure of        M^(III)NbO₄, M^(III)TaO₄, or M^(III)VO₄; or formula ABO₄, where        A is Y or a rare earth and B is Nb, Ta or V,    -   iv) spinel or spinel derived structure of MgAl₂O₄, ZnAl₂O₄,        MnAl₂O₄, CoAl₂O₄,    -   v) a rock salt structure of MgO, CaO, SrO, or NiO, or    -   vi) rutile AO₂ structure, wherein A is Ti or Sn,    -   or a mixture thereof or a solid solution thereof.

Typically, the insulating composition proximate to the frame are any ofthe compositions recited above except for spinel, spinel derivedstructures, inverse spinel, rock salt structure, or corundum.

In one aspect, the insulating oxide ceramic is not Yttria stabilizedzirconia or lanthanium zirconate. In another aspect, the insulatingoxide ceramic is not a pyrochlore or distorted pyrochlore.

In a further aspect, the pyrochlore group includes Nd₂Zr₂O₇, Gd₂Zr₂O₇,Eu₂Zr₂O₇, Y₂Zr₂O₇, Y₂Sn₂O₇, Nd(RETH)₂Sn₂O₇ and solid solution of thesecompositions. Nd₂Zr₂O₇ and at least RETH such as Gd and Eu have thermalexpansion in the region of interest (see FIG. 1) and other RETH earthcation zirconates and stannates and their solid solutions (including La,Y and Sc) also have useful thermal expansion coefficients. In FIG. 1circles represent YSZ, squares represent Neodymium zirconate, starsrepresent Gadolinium zirconate, plusses (+) represent Lantinum zirconateand inverted triangles represent Europium zirconate. FIG. 2 illustratesthe high electronic plus ionic resistivity that can be found in thesecompounds. In FIG. 2 dark circles correspond to 10⁻³ bar oxygen, andwhite circles to 1 bar oxygen.

In another aspect the pyrochlore is M₂Ti₂O₇, wherein M is Sc, Y, La, andall lanthanides except Pm.

The terminology for perovskite and distorted perovskite crystalstructure and superstructure of perovskite is from A. F. Wells,“Structural Inorganic Chemistry,” Fourth edition, Clardon Press, Oxford,1975, pg. 486. Perovskite and distorted perovskite crystal structure andsuperstructure of Perovskite compositions and synthesis of suchcompositions and other compositions for use in this invention can befound in Wells, “Structural Inorganic Chemistry,” cited above and inFrancis S. Galasso, “Structure, Properties, and Preparation ofPerovskite Type Compounds,” Pergamon Press, 1969, both references areherein incorporated by this reference in their entireties and for theirteachings of such compositions.

Some perovskites have high expansions, although most have been studiedfor their dielectric properties for use in capacitors in electronics atnear room temperature. In one aspect, they are Ba(Sr)Zr(Hf)O₃ orBa(Sr){Mg_(1/3)Ta(Nb)_(2/3)}O₃. The oxides of Ba, Sr, Mg, Zr, Hf and Taare not easily reduced so high electrical resistivity are achieved athigh temperatures even in moderately reducing environments.

In another aspect, perovskite composition family's based on BaTiO₃,SrTiO₃, Bi₄Ti₃O₁₂, or Al₂TiO₃ are included. Bi₄Ti₃O₁₂ can have a roomtemperature resistivity of greater than 10⁸ to 10¹² ohm-cm for adeposited film. For compositions containing titanium oxide andparticularly for the bismuth oxide containing compositions, thematerials can preferably be used on the air/cathode side of the fuelcell to avoid reduction of the titanium oxide/bismuth oxide. Aluminumtitanate (Al₂TiO₃) has a very anisotropic thermal expansion coefficientand can microcrack heavily at large grain sizes. With perovskite,distorted perovsike and distorted pyrochlores with anisotropic thermalexpansion coefficients, deposition and sintering techniques which keepthe grain size small are preferred. Grain sizes under 5 microns and morepreferably under 1 microns are preferred for materials with highlyanisotropic thermal expansion coefficients.

In one aspect, fluorite crystal structures and distorted fluoritecrystal structures (tetragonal structures) are of particular interest.Zirconia and hafnia based materials with fluorite/distorted fluoritecrystal structures can be made with very low oxygen vacancyconcentrations. The low vacancy concentration reduces very substantiallythe oxygen ion conduction without increasing electronic conduction. Onemethod to achieve this is to use zirconia (or hafnia) and Y(RETH)TaO₄and/or Y(RETH)NbO₄ to form ceramic solid solutions and alloys withtetragonal and tetragonal prime phases (slightly distorted fluoritecrystal structures). These phases can have very low oxygen ionconductivity and low electronic conductivity while maintaining therelatively high thermal expansion coefficients of the zirconia (hafnia)base material.

FIG. 3 shows the total resistivity as a function of the molar ratio of(M⁵⁺cations +2×M⁶⁺ cations)/(M³⁺ cations+2xM²⁺cations). The thermalexpansion coefficient of these materials is also within 9×10⁻⁶/° C. to15×10⁻⁶/° C. as shown in FIG. 4, where the data has been extrapolatedfrom 800° C. to 1,000° C. With these fluorite systems, alloying withCaWO₄, MgMoO₄ and other combinations and permutations of +2, +6 and +3,+5 cations such as Ca, Mg, W, Mo, V, Sc, Y, and Re and +4 cations suchas TiO₂, SnO₂ and CeO₂ can be useful. The goal is to have a minimum ofoxygen vacancies yet avoid transformation to the monoclinic phase, asthe transformation from a tetragonal phase to monoclinic phase usuallyinvolves generation of cracks which would compromise the insulationability of the layer or coating. This phase transformation also reducesthe effective thermal expansion coefficient due to the volume expansion.In the situation where the coating or layer is exposed to very reducingatmosphere, (i.e. raw fuel), the effect of the reduction on any variablevalance cation as is listed above should be measured and insure that thealloy/compound does not become an ionic or electronic conductor due tothe reduction.

FIG. 5 shows an approximate phase diagram at 1400-1500 C of the ZrO₂(HfO₂)—Y(RETH)Nb(Ta)O₄—Y₂O₃(RETH₂O₃) system (where RETH is a rare earthelement in cation form, including Y and Sc) based on room temperaturetoughness measurements along with x-ray diffraction, and electrondiffraction (for a small number of compositions), naked eye, opticalmicroscopic, SEM and TEM observations. The preferred compositions inthis system for the purpose of electronic and ionic insulation are thosealong and near the ZrO₂—YTa(Nb)O₄ join that have a atomic ratio of +5cations to +3 cations greater than 0.5 and preferably greater than 0.8,more preferably 0.9 and most preferably 1.0 or greater. The tetragonalprime phase and tetragonal phase, both distorted fluorite structures arethe major crystal structure in this composition range. When the alloycontains +6 and +2 cations as well, the ratio is 2×atomic % of +6cations +atomic % of +5 cations divided by 2× the atomic % of +2cations+the number of +3 cations. It is desirable to achieve maximumtoughness without microcracking. In FIG. 5 the dark circles correspondto microcracked and light (unfilled) circles correspond to theunmicrocracked system. The letters A through L correspond to fracturetoughness of 2 through 17, respectfully, where fracture toughness is(K_(1C)) in MPa m^(1/2), rounded to the nearest whole number for thegiven composition(s). The different shaded areas of FIG. 5 indicatephase of the system (ZrO₂—YNbO₄—YO_(3/2)), at room temperature, aftersintering at 1300-1600° C., where: symbol I indicates that material istetragonal after sintering and converts to monoclinic on cooling to roomtemperature; symbol II indicates that material is tetragonal at roomtemperature; symbol III indicates that material is a mixture oftetragonal and cubic at room temperature; and symbol IV indicates thatmaterial is primarily cubic at room temperature.

The invention includes insulating fluorite (distorted fluorite) crystalstructure containing compounds with thermal expansions in variousaspects of 8×10⁻⁶ to 16×10⁻⁶ C, 9.0×10⁻⁶ to 15×10⁻⁶/C, or 9.5×10⁻⁶ to14.5×10⁻⁶/C. In another aspect, insulating fluorite (distorted fluorite)containing compositions with resistivities higher than 100 ohm-cm areused with resistivities higher than 1,000 ohm-cm more and resitivitieseven greater than 10,000 ohm-cm. In another aspect, the fluorite majorphase is tetragonal or tetragonal prime (un-transformable tetragonal).

In further specific embodiments, examples of compositions areNd(RETH)₂Zr₂O₇, Nd(RETH)₂Sn₂O₇, Ba(Sr)Zr(Hf)O₃,Ba(Sr){Mg_(1/3)Ta(Nb)_(2/3)}O₃, BaTiO₃, SrTiO₃, B4Ti₃O₁₂, aluminumtitanate and Zr(Hf)O₂—Y(RETH)Ta(Nb)O₄ composition families.

In other aspects, the insulating oxide ceramic comprises RETHZr₂O₇,RETHSn₂O₇, Ba(Sr)Zr(Hf)O₃, Ba(Sr){Mg_(1/3){Ta(Nb)_(2/3)}O₃, Ba(Sr)TiO₃,Bi4Ti₃O₁₂, Al₂TiO₃, or ZrO₂—HfO₂ with RETH (Mg or Ca)Ta(Nb)O₄. In otheraspects, the insulating oxide ceramic comprises Nd(RETH)₂Zr₂O₇,Nd(RETH)₂Sn₂O₇, Ba(Sr)Zr(Hf)O₃, Ba(Sr){Mg_(1/3)Ta(Nb)_(2/3)}O₃, BaTiO₃,SrTiO₃, Bi₄TiO₁₂, Al₂TiO₃, Zr(Hf)O₂—Y(RETH)Ta(Nb)O₄, La₂Zr₂O₇, Nd₂Zr₂O₇,Gd₂Zr₂O₇, Eu₂Zr₂O₇, Y₂Zr₂O₇, or Y₂Sn₂O₇, where RETH is a rare earthelement including Y and Sc.

In another aspect, the insulating composition can compriseNd(RETH)₂Zr₂O₇ and Zr(Hf)O₂—Y(RETH)Ta(Nb)O₄ composition families, whereRETH denotes rare earth cations, including Y and Sc.

In other aspects, the insulating composition can comprise RETHZr₂O₇,RETHSn₂O₇, or mixtures thereof. In other aspects, the insulatingcomposition can comprise ZrO₂—HfO₂ with RETH (Mg or Ca)Ta(Nb)O₄. Inother aspects, the insulating composition can comprise Ba(Sr)Zr(Hf)O₃ orBa(Sr){Mg_(1/3){Ta(Nb)_(2/3)}O₃.

In another aspect, the ordered anion defective fluorite can beZr₅Sc₂O₁₃.

The insulating compositions of the invention can be combined with wellknow high temperature insulators, such as alumina and magnesiumaluminate spinel, at volume fractions of the insulating compositions ofthe invention of, for example, from about 25% to about 95 vol. %, orfrom about 45% to about 95 vol. %, to increase the thermal expansioncoefficient to better match the CTE of the frame, while maintaining thecomposite materials insulating properties.

Second phases such as alumina are often used in ceramics whose mainphase is fluorite crystal structure as a grain growth inhibitor or atoughening agent. For some compositions with primary phases ofpyrochlores and perovskites, alumina and other oxides can be used asgrain growth inhibitors or as toughening agents. In one embodiment, upto 5 volume % of a second phase oxide insulating phase is used.

In one embodiment, the insulation compositions of the invention can havethermal expansion coefficients of from 8.0 to 16.0×10⁻⁶/° C. from roomtemperature-1000° C., in another aspect from 9×10⁻⁶ to 15×10⁻⁶/° C. andin another aspect from 9.5×10⁻⁶ to 14.5×10⁻⁶/° C. The insulatingcompositions can restrict both electronic and ion conduction. Theinsulation systems can have low electronic and ionic conduction in atleast in air, and in another aspect, in both air and reducingenvironments, at temperatures of from about 500 to 1000° C.

In various aspects, the insulating composition has a resistivity of atleast 10 ohm-cm, at least 100 ohm-cm, at least 1,000 ohm-cm, or at least10,000 ohm-cm. In various aspects, the insulating composition has anarea specific resistance of at least 10 ohm-cm², at least 100 ohm-cm²,at least 1,000 ohm-cm², or at least 10,000 ohm-cm². Such resistivitiescan be found in both high oxygen activity and somewhat reducingenvironments.

The compositions of the invention are commercially available or arereadily synthesized. For a general synthesis, see for example, A. F.Wells, “Structural Inorganic Chemistry,” Fourth edition, Clardon Press,Oxford, 1975 and Francis S. Galasso, “Structure, Properties, andPreparation of Perovskite Type Compounds,” Pergamon Press, 1969.

Depending upon the problem to be solved by the use of the insulatingoxide and the geometry of how the material is used, the line resistanceor aerial resistance of the layer or region can be a designconsideration. Thin layers on electrically conducting frames for examplemay need to have an area specific resistance of greater than 10,000ohms-cm² to prevent seal degradation, while insulators as a coating oras an insulating region in an electrolyte used to prevent power loss mayonly need a resistivity of about 10 ohm-cm or an area specificresistance of 10 ohm-cm². Regions in the electrolyte sheet thatelectronically and ionically isolate the cells on the sheet can have alower resistance for a power loss use, but may need a high resistance toprevent current flow and seal degradation over the extended times,thousands to perhaps tens of thousands of hours, the lengths somecommercial SOFC systems are expected to operate.

The geometry of the insulating material multiplied by the resistivity ofthe material leads to the resistance per length or area. For preventionof seal degradation, in certain aspects, a resistance of 10,000 ohms-cm²may be desired. Table I below shows what combinations of resistivity andthickness can lead to an areal resistance of greater than 10 ohm-cm²(single asterisk) or even greater than 10,000 ohms-cm² (doubleasterisk). The asterisks in the table indicate the acceptable rangedepending on the use for certain aspects of the invention. It differsfor each use, with the metal coatings being the most stringent. Forreducing power loss, relatively thin coatings, on the order of 100microns and materials with resitivities of 1,000 ohm-cm at the operatingtemperature can be employed (see single asterisked combinations). Forthe more stringent goal of reducing seal degradation, thicker coatingsand or more resistive materials need to be used (see double asteriskedcombinations). See FIG. 17 for an example of these aspects.

For preventing power loss or material degradation to the seal when usinginsulating oxides through the thickness of the electrolyte, a widevariety of material resisitives may be employed, due to the slightthickness of the electrolyte. For an example of this, see FIGS. 15 a andb and 16 a and b. Table II below shows the linear resistance expected atlength scales appropriate between cell/via pads and cell. Table IIIbelow shows the linear resistance expected at larger length scaleappropriate for the street widtk region of electrolyte between the cellsand the seal. For the purposes of the calculation in Tables II and III,the electrolyte (and insulating region thickness) is assumed to be 20microns thick. For Tables II and III, single asterisk denotes 10 cm-ohmor higher and a double asterisk denotes 10,000 cm-ohm or higher.

For prevention of power loss between electrodes in multiple celldevices, a resistance of about only 10 ohms-cm may suffice. See, forexample, FIG. 13 for this aspect. Table III shows the combinations ofresistivity, thicknesses and separation distance to achieve thisresistance. When the inventive materials are used through the thicknessto prevent power loss or seal degradation, lower resistivity materialscan be used. For a coating on an electrolyte of only 1-25 microns inthickness, the higher resistivity materials are desirable, particularlyfor the 10,000 ohm-cm² criteria as shown in Table IV below. Table IVbelow shows what combinations of resistivity and thickness can lead toan areal resistance of greater than 10 ohm-cm² (single asterisk) or evengreater than 10,000 ohms-cm² (double asterisk). For reduction of thepower/efficiency loss associated with via-region short-circuiting, aresistive layer of about 10 ohm-cm² or more will essentially eliminatethe problem. Such layers may be easily introduced under each via pad. Anexample of such a printed pattern shown in FIG. 12 b.

For under the via pad or bus bar or in the via gallery, in one aspect,the thickness is from 0.1 micron to 100 microns, in another aspect from1 to 10 microns. For the frame coatings, in one aspect, the thickness isfrom 1 to 1000 microns, in another aspect from 10 to 100 microns. Forprevention of power loss via insulating oxides through the thickness ofthe electrolyte, in one aspect, the width of diffused area (path length)is from 0.05 cm to 5 cm and in another aspect is from 0.2 cm to 1 cm.

TABLE I Areal resistance for a coating, in ohm - cm² Coating Materialresistivity ohm -cm thickness, cm 100 1,000 10,000 100,000 1,000,0000.01 1 *10 *100 *1,000 **10,000 0.05 5 *50 *500 *5,000 **50,000 0.1 *10*100 *1,000 **10,000 **100,000 0.5 *50 *500 *5,000 **50,000 **500,000 1*100 *1,000 **10,000 **100,000 **1,000,000 2 *200 *2,000 **20,000**200,000 **2,000,000

TABLE II Linear resistance in ohm - cm, length scales appropriate forcell/via gallery spacing Insulation region Material resistivity ohm -cmlength, cm 100 1,000 10,000 100,000 1,000,000 0.001 *50 *500 *5,000**50,000 **500,000 0.005 *250 *2,500 **25,000 **250,000 **2,500,000 0.01*500 *5,000 **50,000 **500,000 **5,000,000 0.025 *1,250 **12,500**125,000 **1,250,000 **12,500,000 0.05 *2,500 **25,000 **250,000**2,500,000 **25,000,000

TABLE III Linear resistance in ohm - cm, length scales appropriate forinsulating street width spacing Material resistivity ohm -cm Length, cm100 1,000 10,000 100,000 1,000,000 0.1 *5,000 **50,000 **500,000**{grave over ( )}5,000,000 **50,000,000 0.5 **25,000 **250,000**2,500,000 **25,000,000 **250,000,000 1 **50,000 **500,000 **5,000,000**50,000,000 **500,000,000 2 **100,000 **1,000,000 **10,000,000**100,000,000 **1,000,000,000

TABLE IV Areal resistance in ohm - cm² Thickness, Material resistivityohm -cm cm 100 1,000 10,000 100,000 1,000,000 0.001 0.1 1 *10 *100*1,000 0.005 0.5 5 *50 *500 *5,000 0.01 1 *10 *100 *1,000 **10,000 0.0252.5 *25 *250 *2,500 **25,000

In one aspect, the insulating composition is proximate to the bus barand/or via pad. In another aspect, the insulating composition is incontact with the bus bar and/or via pad. In another aspect, theinsulating composition is in contact with the electrolyte. In anotheraspect, the insulating composition is in contact with the bas bar andthe electrolyte.

In another aspect, the insulating composition is in contact with the viapad and the electrolyte. In another aspect, the insulating compositionis in contact with two or more via pads and the electrolyte. In anotheraspect, the insulating composition is a continuous layer in contact withtwo or more via pads and the electrolyte.

In another aspect, the insulating composition is present in part of theelectrolyte. That is, the insulating composition forms part of theelectrolyte sheet. In this aspect, the insulating composition can bepresent across part of the diameter in part of the electrolyte or it canbe present across the entire diameter in part of the electrolyte. Inanother aspect, the insulating composition is present in part of theelectrolyte and is present in at least one discrete section. In anotheraspect, the insulating composition is present in part of the electrolyteand is proximate the seal. In another aspect, the insulating compositionis present in part of the electrolyte and is in contact with the seal.In another aspect, the insulating composition is present in part of theelectrolyte and is not in contact with the seal. In another aspect, theinsulating composition is present in part of the electrolyte and isbetween the electrode and the seal.

In another aspect, the insulating composition is under the via pads,over the electrolyte in the via gallery, through the electrolyte in thevia gallery, under the bus bar, or through the electrolyte under the busbar. In this aspect, in one embodiment, the insulating composition canextend up to 5 mm past these features on the electrolyte with amulti-cell design.

In another aspect, the insulating composition is adjacent to and incontact with the frame. In this aspect, the insulating composition canbe disposed between the frame and the seal, wherein the seal is disposedbetween the insulating composition and the electrolyte.

In yet another embodiment, the insulating composition is not in contactwith the cathode and/or anode.

The insulation composition, layers, and coatings can be used in any fuelcell device in the art. Fuel cell designs are well known to those ofskill in the art. Representative examples of a fuel cell device forwhich the insulation of the present invention can be readily applied isfound in U.S. Pat. No. 6,623,881 to Badding et al., U.S. Pat. No.6,630,267 to Badding et al., and U.S. Pat. No. 6,852,436 to Badding etal., which are all herein incorporated by this reference in theirentireties and are all incorporated by this reference specifically forthe teaching of the configuration of a fuel cell device.

In a typical configuration of a SOFC herein, the electrolyte is disposedbetween the anode and the cathode, the anode of one fuel cell iselectrically connected to the cathode of another fuel cell by a via padat the anode and a via pad at the cathode, the via pads are electricallyconnected to each other with a via fill that traverses through theelectrolyte, the bus bar is electrically connected to the electrode ateach end of the electrolyte, and the seal is disposed between theelectrolyte and a frame adjoining the seal. Typically, the seal is incontact with the electrolyte (or the insulation portion of theelectrolyte). In one aspect, the seal is in contact with the frame, andin another aspect, the seal is not in contact with the frame. When notin contact with the frame, the seal can instead be in contact with, forexample, the insulation layer on the frame as in FIG. 17. In one aspect,the electrolyte is an unsupported, free standing sheet. The electrolytethickness is typically ≦30 μm, such as from 4 μm to 30 μm. Maintainingtotal internal fuel cell resistances at values less than 1 ohm-cm², oreven below 0.6 ohm-cm², at designed operating temperatures is important,and to achieve such values the electrical resistance of the electrolytesheet should be less than 0.5 ohm-cm², preferably less than 0.3 ohm-cm².For conventional oxygen-ion-conducting electrolytes this means that,depending on cell operating temperature, sheet or plate thickness willgenerally be below 1 mm, with sheet thicknesses in the 100-500 μm rangebeing preferred where the electrolyte is to impart some structuralrigidity to electrode/electrolyte structure.

The electrolyte, anode, and cathode materials can be those typicallyused in the art. In various non-limiting examples, those materials areas disclosed in U.S. Pat. No. 6,623,881 to Badding et al., U.S. Pat. No.6,630,267 to Badding et al., and U.S. Pat. No. 6,852,436 to Badding etal., which patents are al herein incorporated by this reference for allof their teachings as well as specifically for their teachings of theelectrolyte and electrode materials. For example, in one embodiment, theelectrolyte is 3YSZ, the cathode catalyst is LSM/YSZ, the cathodecurrent collector is Ag—Pd/ceramic, the anode catalyst is Ni/YSZ, andthe anode current collector is Ag—Pd/ceramic. This invention is notlimited to these and may apply to doped ceria and gallia basedelectrolytes and compounds of such, such as gadolinium doped ceria andlanthanum gallate, and electrode compositions found to be useful forthose electrolytes known to those skilled in the art.

Referring to FIG. 9 a, which is one embodiment of the invention, a fuelcell sheet or device is shown (10). The sheet or device contains 10 fuelcells. The fuel cell device comprises an electrolyte sheet (20) and anelectrode cell (30). The electrode cell (30) is contained on each sideof the electrolyte sheet (20). The bus bars are shown at (40) and themetal filled via current path at (50). A blow up of the metal filled viacurrent path is shown in FIG. 9 c. The electrolyte sheet showing the viaholes that contain the vias are shown in FIG. 9 d.

FIG. 9 b is an overall representation of a typical fuel cell device ofthe invention. The electrolyte (20) is disposed between the cathode orcathode catalyst layer (60) and anode or anode catalyst layer (80) andthe cathode (60) is in contact with the cathode current collector (70)and the anode (80) is in contact with the anode current collector (90).Oxygen typically from air enters the cathode current collector (70) andexits the anode current collector (90) after reacting with hydrogen inthe fuel to form water.

FIG. 10 is a side view of cut line A-A of FIG. 9 a. The electrolyte (20)is shown in electrical communication with the cathode catalyst layer(60), cathode current collector (70), anode catalyst layer (80), andanode current collector (90). Additionally, the bus bar (100) is shownat one end of the fuel cell in electrical communication with the cathodecurrent collector (70). The metal filled via (110) connects each of thevia pads (50) and (51) so that current can flow from the anode currentcollector of one cell (90) to the cathode current collector (70) of thenext cell. The insulating layer of one embodiment of the invention isshown at (120), (121), wherein the insulating layer (120) and/or (121)is disposed between the via pad (50) and/or (51) and the electrolyte(20). In another embodiment, the insulating layer (130) is disposedbetween the bus bar and the electrolyte (20).

FIG. 11 is a cross sectional view taken along cut line B-B of FIG. 9 a.The cathode (60), cathode current collector (70), anode (80), anodecurrent collector (90), and electrolyte (20) are all shown with similarrepresentation as in FIG. 10. The metal filled via (110) is connectedfrom one via pad (50) to another via pad (51) through the electrolyte(20). The insulating layers (120) and (121) in one embodiment are shownbetween the via pad (50) and electrolyte (20) and via pad (51) andelectrolyte (20).

FIGS. 12 a and 12 b show approximate locations for the insulatingcomposition for one aspect of the invention. Specifically, in FIG. 12 a,the fuel cells are shown as one unitary system (10), containing theelectrolyte sheet (20), the via pads (50), (51), bus bars (100), (101),and electrodes (140). FIG. 12 b shows the approximate locations for thearea for the insulating layers under the via pad (122) and bus bar(123), respectively, extending out slightly. A similar pattern butreversed can be on either side of the electrolyte (20).

FIG. 13 shows another embodiment of the invention where the insulatingregions or layers are shown in the via galleries (124) as a uniformlayer on the electrolyte sheet (20) and under the bus bar (125). Asimilar pattern can be reversed on the other side of the electrolyte(20).

FIG. 14 shows another aspect of the invention comprising a frameassembly (230) with two fuel cell devices (210), (220) to form a packet(200) of one embodiment of the present invention. The frame can be madeof a variety of materials, such as those used in the art, for example,metallic compositions such as stainless steel. The fuel cell devices(210), (220) are fixed to the frame (230) by any seal, such as onetypically used in the art, such as for example, glass or glass ceramicseals.

FIG. 15 shows another embodiment of the present invention. In thisembodiment part of the electrolyte (20) is made of the insulatingmaterial. In FIG. 15 b, the frame (300), seal (310), and electrolyte(20) are shown. The part of the electrolyte (20) formed from theinsulating material is shown as (320). The insulating material in theelectrolyte (20) can be across the entire diameter of the electrolytethickness as shown in FIG. 15 b or may only traverse part of thediameter of the electrolyte (20) (not shown). FIG. 15 a is a top levelview of the FIG. 15 b configuration, showing the electrolyte (20), thesealed region (310), which forms a race track type configurationadjoining the frame (300) to the electrolyte (20). The insulating regionwithin the electrolyte (320) is shown. The electrode (not shown) in FIG.15 b is to the right of the insulating region (320), and therefore, theinsulating region (320) is disposed between the electrode and the seal(310).

FIG. 16 is another embodiment of the invention, and shows aconfiguration similar to FIG. 15 b except that the insulating region(321) is displaced away from the seal region (310) and is not in contactwith the seal (310). The electrode (not shown) in FIG. 16 b is to theright of the insulating region (321), and therefore, the insulatingregion (321) is disposed between the electrode and the seal (310).

FIG. 17 shows yet another embodiment of the invention. Here the frame(400) is joined to the electrolyte (20) with a seal (310). An insulatingcoating (410) is disposed between the seal (310) and the frame (400).The insulating coating can extend about the width of the seal (310) (notshown) or further outside of the seal (310), up to and including aroundthe frame (400) as shown in FIG. 17.

The fuel cell can be part of a sheet or device, which in turn can becombined with another sheet or device to form a packet, which packet inturn can be combined with other packets to form a stack. Such a stackcan be part of a larger fuel cell system. In one aspect, there are atleast two cells on the electrolyte.

The insulating composition is typically applied to the electrolyte belowor adjacent to the bus bar and via pads by screen printing, althoughother methods are applicable. Thicker layers are possible and thinnerlayers are possible with other coating methods, such as ink jet,photolithography, e-beam deposition, sputtering, CVD, sol gel, PVD, etc.The insulating materials of the invention can be used in SOFC systems ascoatings on conducting frames, applied by a variety of means includingplasma spraying, e-beam deposition, electrophoresis, sol-gel coating,slurry coating, etc. For a solid oxide fuel cell wherein the insulatingcomposition is present in part of the electrolyte and optionally theinsulating composition is present across part of the diameter or theentire diameter in part of the electrolyte, a coating may be applied tothe pre-fired electrolyte and the insulating material in the insulatingarea may be formed by diffusion of coating constituents into theelectrolyte or by interdiffusion between the coating constituents andthe electrolyte. Alternately, the material may be applied to the unfiredelectrolyte, and diffused to form the insulating region.

In one aspect, to make a useful patterned insulating layer, such as, forexample a rare earth zirconate, on a zirconia electrolyte, a rare earthoxide or oxide precursor is patterned on the surface of the electrolyteand the oxide reacts at high temperature to form an insulatingpyrochlore phase.

The compositions of the invention can be used in SOFC systems ascoatings on conducting frames to prevent power loss and electrochemicaldegradation of the seal, on or through the electrolyte to prevent powerloss between cells in systems with a single or multiple cell device on asingle electrolyte as well as preventing stray electrochemical reactionsthat can degrade the materials. These compositions can be used on orthrough the electrolyte to prevent power loss from the active region(with the electrodes) to the frame as well as electrochemical reactionsdegrading the materials, particularly the seal.

The insulating materials of the invention can be used in SOFC systems ascoatings on conducting frames. Such coatings are particularly usefulwhen the fuel cell design includes multiple cells on one electrolytesheet, as considerable voltages can be generated at the seal by such adesign. While intended as an electrically insulating coating, if thecoating covers all or the majority of a metal frame surface, when themetal contains Cr, the coating can also act to prevent Cr migration tothe cathodes of the fuel cell and reduction of fuel cell electrodeperformance. When the coating is nearly matched in thermal expansion tothe frame, the coating's thickness can be quite large, such as forexample, 250 microns, 500 microns, or even up to 1 mm.

The composition families can also be used on the electrolyte sheet asinsulating layers. Areas of the electrolyte sheet that can employ theseinsulating composition layers are the perimeter of the sheet between theion conducting electrolyte sheet and the seal material and underneaththe bus bars and under the via pads or in the via galleries in amulti-cell device design as shown in FIGS. 12 a and 12 b and 13.

The insulation compositions of the present invention have improvedmechanical strength, decreased mechanical failure, and/or an improvedCTE match to the frame of the packet. This invention can be used as acoating material on a conducting frame in a variety of thicknesses, asthe inventive compositions can have a better thermal expansion match tothe frame materials than alumina. The insulating structures will notreact with glasses and glass ceramic seals as easily as the magnesia inthe magnesium aluminate spinel plus magnesia coating of the prior art.

The insulating oxide materials can be used as coatings on theelectrolyte. When the expansion coefficient and sintering properties arematched well enough, the materials can also be used as part of theelectrolyte, even through the entire thickness in some regions of theelectrolyte. The inventive compositions can also be used as a reactionbarrier layer between other insulating coatings such as magnesiumaluminate spinel plus magnesia and glass seals to prevent reaction withthe seal material. As magnesium aluminate spinel plus magnesia is a veryinexpensive material, a reaction barrier layer of the inventiveinsulating non-reactive oxides on magnesium aluminate spinel plusmagnesia can be an attractive composite insulating coating/material.

The compositions of this invention also have a CTE advantage over priorinsulation compositions. This is due in part to the thermal expansioncoefficient of alumina (about 88×10⁻⁷/C) being quite different than theexpansion of the frames and electrolyte, (about 105 to 125×10⁻⁷/C),inducing stresses in the plasma sprayed alumina (PSA) layer on thermalcycling, whereas the compositions of the present invention are wellmatched to the CTE of the frames and electrolyte.

Although several aspects of the present invention have been described inthe detailed description, it should be understood that the invention isnot limited to the aspects disclosed, but is capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

EXAMPLES

To further illustrate the principles of the present invention, thefollowing examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompositions, articles, devices, and methods claimed herein are made andevaluated. They are intended to be purely exemplary of the invention andare not intended to limit the scope of what the inventors regard astheir invention. Efforts have been made to ensure accuracy with respectto numbers (e.g., amounts, temperatures, etc.); however, some errors anddeviations should be accounted for. Unless indicated otherwise,temperature is ° C. or is at ambient temperature, and pressure is at ornear atmospheric. There are numerous variations and combinations ofprocess conditions that can be used to optimize product quality andperformance. Only reasonable and routine experimentation will berequired to optimize such process conditions.

Example 1

ZrO₂ with approximately 16 mole % YTaO₄ and approximately 0.5 mol %Ta₂O₅ composition, was made and applied to a zirconia-3 mole % yttriaelectrolyte. The yttrium tantalate doped zirconia composition has adistorted fluorite structure, T′ (tetragonal prime) phase, as its majorphase. Zirconia-8 mole % yttria powder, Tosho TZ-8Y, was vibro-milledwith the appropriate amount of Ta₂O₅ for several days using ethanol as afluid and using Tosho TZ3Y milling media. The powder was dried andcalcined at about 120° C. for several hours in air. The powder wasvibro-milled a second time for 24 hours. After drying, NiO was added asa sintering aid at the <5 wt % level and the powder made into inks usinga three roll mill. The composition was screen printed onto zirconia3-mole % yttria electrolyte and the sample dried, then fired at about1400° C. for several hours in air. The phases in the sample wereidentified by x-ray diffraction, FIG. 6, and found to be a zirconiayttrium tantalate phase along with a very small amount of NiO, alongwith the underlying tetragonal zirconia electrolyte. In FIG. 6 thedashed line corresponds to 89-9068 Zirconia (Ydoped),syn-(Zr_(0.94)Y_(0.06))O_(1.88); the dotted line corresponds to43-0308-Zr_(0.66)Y_(0.17)Ta_(0.17)O₂-Tantalum Yttrium Zirconium Oxideand a sold line corresponds to 89-7390-Bunsenite, synthetic NiO. Thenumbers 17-0458 and 43-0308 are crystal phase identifiers, and arediffraction file numbers, available for example, from PDF4 diffractiondatabase. The PDF4 database is distributed by the International Centerfor Diffraction Data (ICDD). The d-space values are provided inangstroms (A)). SEM examination of fractured and polished sectionsshowed a well defined layer about 1-3 microns thick with some porosityon the surface of the electrolyte, FIGS. 7 a and 7 b. No sign ofmicro-cracking or monoclinic zirconia was noted in x-ray diffraction orSEM. With process modification, the layer can have a minimum of porositythat extends through the layer at any substantial amount of the area ofthe coating or be closed porosity or dense. Thicker layers are possibleand thinner layers are possible with other coating methods, such ase-beam deposition, sputtering, CVD, sol gel, PVD, etc.

Example 2

For Nd₂Zr₂O₇ layers, NdCO₃ was calcined to Nd₂O₃. The Nd₂O₃ was milledwith undoped zirconia powder TZ-0Y, Tosho, using vibro-milling in anethanol fluid with Tosoh TZ3Y zirconia media. After drying, the milledpowder was reacted at about 120° C. for several hours in air. The powderwas vibro-milled a second time for 24 hours. After drying, the powderwas made into inks using a three roll mill. The composition was screenprinted onto zirconia 3-mole % yttria electrolyte and the sample dried,then fired at ˜1400 C for several hours in air. The phases in the samplewere identified by x-ray diffraction, FIG. 8 a, and found to be apyrochlore neodymium zirconate phase along with the underlyingtetragonal zirconia electrolyte. The d-space values are provided inangstroms (A)). The numbers 17-0458 and 89-9068 are crystal phaseidentifiers, and are diffraction file numbers, available for example,from PDF4 diffraction database. In FIG. 8A the sold line corresponds tothe 17-0458-Nd₂Zr₂O₇ Neodimium Zirconium Oxide, and the dashed linecorresponds to 89-9068-Zirconia (Ydoped), synthetic(Zr_(0.94)Y_(0.06))O_(1.88). The 7.18 A and possibly 2.84 A peak is froma clay sample support. SEM examination of fractured and polishedsections showed a well defined layer about 10 microns thick withporosity, FIG. 8 b. A thin 1 micron fully dense layer was found betweenthe neodymium zirconate and the underlying zirconia 3-mole % yttriaelectrolyte. This thin dense layer could be neodymium zirconate or acubic zirconia with a mixed yttrium oxide, neodymium oxide stabilizer.No sign of micro-cracking or monoclinic zirconia was noted in x-raydiffraction or SEM. With process modification, the neodymium zirconatelayer can have a minimum of porosity that extends through the layer atany substantial amount of the area of the coating, be closed porosity ordense. Thicker layers are possible and thinner layers are possible.Other coating methods, such as e-beam deposition, sputtering, CVD, etc.can be utilized.

Various modifications and variations can be made to the compositions,articles, devices, and methods described herein. Other aspects of thecompositions, articles, devices, and methods described herein will beapparent from consideration of the specification and practice of thecompositions, articles, devices, and methods disclosed herein. It isintended that the specification and examples be considered as exemplary.

1. A solid oxide fuel cell comprising a cathode, an anode, anelectrolyte, a bus bar, a via pad, a seal, and an insulating amount ofan insulating composition, wherein the insulating composition isproximate to the bus bar and/or the via pad and/or is present in part ofthe electrolyte, wherein the insulating composition is not substantiallydisposed between the cathode and the electrolyte.
 2. A solid oxide fuelcell comprising a cathode, an anode, an electrolyte, a bus bar, a viapad, a seal, and an insulating amount of an insulating composition,wherein the insulating composition is proximate to the bus bar and/orthe via pad and/or is present in part of the electrolyte, wherein theinsulating composition is not lanthanum zirconate or strontiumzirconate.
 3. The solid oxide fuel cell of claim 2, wherein theinsulating composition is not a rare earth zirconate or an alkalineearth zirconate.
 4. A solid oxide fuel cell comprising a cathode, ananode, an electrolyte, a bus bar, a via pad, a seal, and an insulatingamount of an insulating composition comprising one or more insulatingoxide ceramics having the following crystal structure class, superclass, derivative structure or superstructure of the following crystalstructure type: i) pyrochlore or distorted pyrochlore, ii) perovskite,distorted perovskite, superstructure of perovskite, or interleavedperovskite-like structure, iii) fluorite, distorted fluorite, fluoritelike, anion defective fluorite, sheelite, fergusonite, or fluoriterelated ABO₄ compound, iv) spinel, spinel derived structure, or inversespinel, v) rock salt structure, vi) ilmenite, vii) pseudobrookite A₂BO₅,viii) stoichiometric structure based on ReO₃-like blocks, ix) bronze ortetragonal bronze structure based on ReO₃-like blocks, x) rutile; xi)trirutile crystal structure or columbite crystal structure of AB₂O₆,xii) cubic rare earth (C-M₂O₃) structure, or xiii) corundum, or amixture thereof or a solid solution thereof. wherein the insulatingcomposition is proximate to the bus bar and/or the via pad and/or ispresent in part of the electrolyte.
 5. The solid oxide fuel cell ofclaim 4, wherein the insulating composition is proximate to the bus barand/or via pad.
 6. The solid oxide fuel cell of claim 4, wherein theinsulating composition is in contact with the bus bar and/or via pad. 7.The solid oxide fuel cell of claim 4, wherein the insulating compositionis in contact with the electrolyte.
 8. The solid oxide fuel cell ofclaim 4, wherein the insulating composition is in contact with the basbar and the electrolyte.
 9. The solid oxide fuel cell of claim 4,wherein the insulating composition is in contact with the via pad andthe electrolyte.
 10. The solid oxide fuel cell of claim 4, wherein theinsulating composition is in contact with two or more via pads and theelectrolyte.
 11. The solid oxide fuel cell of claim 4, wherein theinsulating composition is a continuous layer in contact with two or morevia pads and the electrolyte.
 12. The solid oxide fuel cell of claim 4,wherein the insulating composition is present in part of theelectrolyte.
 13. The solid oxide fuel cell of claim 4, wherein theinsulating composition is present across part of the diameter in part ofthe electrolyte.
 14. The solid oxide fuel cell of claim 4, wherein theinsulating composition is present across the entire diameter in part ofthe electrolyte.
 15. The solid oxide fuel cell of claim 4, wherein theinsulating composition is present in part of the electrolyte and ispresent in at least one discrete section.
 16. The solid oxide fuel cellof claim 4, wherein the insulating composition is present in part of theelectrolyte and is proximate the seal.
 17. The solid oxide fuel cell ofclaim 4, wherein the insulating composition is present in part of theelectrolyte and is in contact with the seal.
 18. The solid oxide fuelcell of claim 4, wherein the insulating composition is present in partof the electrolyte and is not in contact with the seal.
 19. The solidoxide fuel cell of claim 4, wherein the insulating composition ispresent in part of the electrolyte and is between the electrode and theseal.
 20. The solid oxide fuel cell of claim 4, wherein the insulatingoxide ceramic comprises one or more of i) pyrochlore or distortedpyrochlore crystal structure according to the formula (1) A₂B₂O₇ havingthe valence A³⁺ ₂B⁴⁺ ₂O₇, wherein A³⁺ is Sc, Y, La, Nd, Eu, Gd, or other3+ lanthanide and B⁴⁺ is Zr, Ti, Hf, or Sn, or (2) A₂B₂O₇ having thevalence A²⁺ ₂B⁵⁺ ₂O₇, wherein A²⁺ is Ca, Sr, Zn, or Ba and B⁵⁺ is Nb,Ta, or V, ii) perovskite; distorted perovskite crystal structure;superstructure of perovskite according to the formula ABO₃ (1) havingthe valence A²⁺B⁴⁺O₃, wherein A²⁺ is Mg, Ca, Sr, or Ba and B⁴⁺ is Ti,Zr, Hf, or Sn, (2) having the valence A³⁺13³⁺O₃, wherein A³⁺ is Sc, Y,La, or a 3+ lanthanide and B³⁺ is Al, Ga, Cr, Sc, V, or Y, (3) havingthe valence A²⁺(B³⁺ _(0.5)B⁵⁺ _(0.5))O₃, wherein A²⁺ is Ca, Sr, or Ba,B³⁺ is Al, Cr, Ga, Sc, Y, La, Ce, or other 3+ lanthanide, B⁵⁺ is V, Nb,Ta, or Sb, (4) having the valence A²⁺(B²⁺ _(0.33)B^(5÷) _(0.67))O₃,wherein A²⁺ is Ca, Sr, or Ba, B²⁺ is Mg, Ca, Cd, Ni, or Zn, B⁵⁺ is Nb,Ta, or Sb, (5) having the valence A²⁺(B²⁺ _(0.5)B⁶⁺ _(0.5))O₃, whereinA²⁺ is Ca, Sr, or Ba, B²⁺ is Mg, Ca, Sr, Ba, Cd, Ni, or Zn, B⁶⁺ is Mo, Wor Re, (6) having the valence A³⁺ _(0.33)B⁵⁺O₃, wherein A³⁺ is Y, La,Ce, Pr, Nd, Sm, Gd, Dy, Ho, or Er, B⁵⁺ is Nb or Ta, or (7) having thevalence'A³⁺(B²⁺ _(0.5)B⁴⁺ _(0.5))O³, where A³⁺ is La or a lanthanide,B²⁺is Mg, and B⁴⁺ is Ti, interleaved Bi₂O₂, or perovskite-likestructure, iii) (1) fluorite or distorted fluorite ofA_(1−x−y)B_(x)C_(y)O_(2+/−z), where A is Zr, Hf, or Ce, B is Mg, Ca, Y,Sc, or a rare earth, C is V, Nb, or Ta, where x<1, y<1 and x+y<1, and zdepends upon the valence of B and C, wherein, if B is 2+, thenz=2+0.5y−x, and if B is 3+, then z=2+0.5y−0.5×, (2) a fluorite likecompound of A_(1−x−y)B_(x)C_(y)O_(2+/−z), where A is Zr, Hf, or Ce, B isMg or Ca, and C is W or Mo, where x<1, y<1, x+y<1, and z is 2+y−x, (3) asheelite type structure of ABO₄, where A is Mg or Ca and B is W or Mo,(4) a fergusonite type structure of M^(III)NbO₄, M^(III)TaO₄ orM^(III)VO₄, where M^(III) is a metal of valence +3, or formula ABO₄where A is Y or a rare earth and B is Nb, Ta or V, (5) an aniondefective fluorite, or (6) a fluorite related ABO₄ compound, withvalence A²⁺B⁶⁺O₃ or A³⁺B⁵⁺O₃, wherein A²⁺ is Ca or Ba, B⁶⁺ is Cr, A³⁺ isCr, and B⁵⁺ is Nb, iv) (1) spinel structure or a spinel derivedstructure of AB₂O₄, where A is Mg, Ni, Zn, Co, Fe, or Mn and B is Al,Ga, Cr, or Fe, (2) A₃B₃₂O₅₁, where A is Ca, Ba, or Sr and B is Al, or(3) an inverse spinel or A₂BO₄, wherein A is Mg or Zn and B is Ti or Sn,v) rock salt structure AO, where A is Mg, Ca, Sr, Ba, or Ni, vi)ilmenite of formula ABO₃, wherein A is Ni, Co, Mn or Fe and B is Ti, orgiekielite where A is Mg and B is Ti, vii) pseudobrookite crystalstructure of the formula A₂BO₅, where A is Al or Fe and B is Ti, viii) atetragonal bronze structure based on ReO₃-like blocks or a Nb₂O₅—WO₃mixture, ix) a tetragonal bronze of valence A²⁺B⁵⁺ ₂O₆, wherein A²⁺ isSr or Ba and B⁵⁺ is Nb or Ta, or the superstructure A²⁺ ₅B⁵⁺ ₁₀O₃₀, A²⁺₆B⁴⁺ ₂B⁵⁺ ₈O₃₀, or A²⁺ ₅B³⁺B⁴⁺ ₃B⁵⁺ ₇O₃₀, where A²⁺ is Ca, Sr, or Ba,B³⁺ is La or a lanthanide, B⁴⁺is Ti, and B⁵⁺ is Nb or Ta, x) rutilestructure of AO₂, wherein A is Ti, Sn, or Mn, xi) a trirutile crystalstructure of AB₂O₆, where A is Mg, Cr, or V and B is Ta, W, or Sb; orCaTa₂O₆, xii) a cubic rare earth (C-M₂O₃) structure A₂O₃, where A is Yor a rare earth, or xiii) a corundum structure A₂O₃, where A is Al, Ga,or Cr, or ABO₃, wherein A is Ni and B is Cr, or a mixture thereof or asolid solution thereof.
 21. The solid oxide fuel cell of claim 4,wherein the insulating oxide ceramic comprises one or more of i)pyrochlore or distorted pyrochlore crystal structure of La₂Zr₂O₇,Y₂a₂O₇, Nd₂Zr₂O₇, Gd₂Zr₂O₇, Er₂Zr₂O₇, La₂Hf₂O₇, Y₂Hf₂O₇, Nd₂Hf₂O₇,Gd₂Hf₂O₇, Er₂Hf₂O₇, La₂Sn₂O₇, Y₂Sn₂O₇, Nd₂Sn₂O₇, Gd₂Sn₂O₇, or Er₂Sn₂O₇,ii) perovskite, distorted perovskite crystal structure, superstructureof perovskite, or interleaved perovskite-like structure of SrZrO₃,BaZrO₃, SrHfO₃, BaHfO₃, SrSnO₃, BaSnO₃, BaTiO₃, or SrTiO₃, iii)fluorite; distorted fluorite of A_(1−x−y)B_(x)C_(y)O_(2+/−z), where A isZr, Hf, or Ce and B is Mg, Ca, Y, Sc, or a rare earth and C is V, Nb, orTa where x<1, y<1, x+y<1, y/x>0.5, and z depends upon the valence of Band C, wherein, if B is 2+, then z=2+0.5y−x, and if B is 3+, thenz=2+0.5y−0.5x; fluorite like compound of A_(1−x−y)B_(x)C_(y)O_(2+/−z),where A is Zr, Hf, or Ce, B is Mg or Ca and C is W or Mo, where x<1,y<1, x+y<1, y/x>0.5, and z is 2+y−x; sheelite type structure of ABO₄,where A is Mg or Ca, B is W or Mo; fergusonite type structure ofM^(III)NbO₄, M^(III)TaO₄, or M^(III)VO₄; or formula ABO₄, where A is Yor a rare earth and B is Nb, Ta or V, iv) spinel or spinel derivedstructure of MgAl₂O₄, ZnAl₂O₄, MnAl₂O₄, CoAl₂O₄, or v) a rock saltstructure of MgO, CaO, SrO, or NiO, or vi) rutile AO₂ structure, whereinA is Ti or Sn, or a mixture thereof or a solid solution thereof.
 22. Thesolid oxide fuel cell of claim 4, wherein the electrolyte is disposedbetween the anode and the cathode, the anode of one fuel cell iselectrically connected to the cathode of another fuel cell by a via padat the anode and a via pad at the cathode, the via pads are electricallyconnected to each other with a via fill that traverses through theelectrolyte, the bus bar is electrically connected to the electrode ateach end of the electrolyte, and the seal is disposed between theelectrolyte and a frame adjoining the seal.
 23. A solid oxide fuel cellcomprising a cathode, an anode, an electrolyte, a bus bar, a via pad, aframe, a seal, and an insulating amount of an insulating compositioncomprising one or more insulating oxide ceramics having the followingcrystal structure class, super class, derivative structure orsuperstructure of the following crystal structure types: i) pyrochloreor distorted pyrochlore, ii) perovskite, distorted perovskite,superstructure of perovskite, or interleaved perovskite-like structure,iii) fluorite, distorted fluorite, fluorite like, anion defectivefluorite, sheelite, fergusonite, or a fluorite related ABO₄ compound,iv) ilmenite, v) pseudobrookite A₂BO₅, vi) stoichiometric structurebased on ReO₃-like blocks, vii) bronze or tetragonal bronze structurebased on ReO₃-like blocks, viii) rutile, ix) trirutile crystal structureor columbite crystal structure of AB₂O₆, or x) cubic rare earth (C-M₂O₃)structure, or a mixture thereof or a solid solution thereof, wherein theinsulating composition is proximate to the frame of the solid oxide fuelcell.
 24. The solid oxide fuel cell of claim 23, wherein the insulatingcomposition is adjacent to and in contact with the frame.
 25. The solidoxide fuel cell of claim 23, wherein the insulating composition isdisposed between the frame and the seal, wherein the seal is disposedbetween the insulating composition and the electrolyte.
 26. The solidoxide fuel cell of claim 23, wherein the insulating oxide ceramiccomprises one or more of i) pyrochlore or distorted pyrochlore crystalstructure according to the formula (1) A₂B₂O₇ having the valence A³⁺₂B⁴⁺ ₂O₇, wherein A³⁺ is Sc, Y, La, Nd, Eu, Gd, or other 3+ lanthanideand B⁴⁺ is Zr, Ti, Hf, or Sn, or (2) A₂B₂O₇ having the valence A²⁺ ₂B⁵⁺₂O₇, wherein A²⁺ is Ca, Sr, Zn, or Ba, and B⁵⁺ is Nb, Ta, or V, ii)perovskite; distorted perovskite crystal structure; superstructure ofPerovskite according to the formula ABO₃ (1) having the valenceA²⁺13⁴⁺O₃, wherein A²⁺ is Mg, Ca, Sr, or Ba and B⁴⁺ is Ti, Zr, Hf, orSn, (2) having the valence A³⁺B³⁺O₃, wherein A³⁺ is Sc, Y, La, or a 3+lanthanide and B³⁺ is Al, Ga, Cr, Sc, V, or Y, (3) having the valenceA²⁺(B³⁺ _(0.5)B⁵⁺ _(0.5))O₃, wherein A²⁺ is Ca, Sr, or Ba, B³⁺ is Al,Cr, Ga, Sc, Y, La, Ce, or other 3+ lanthanide, B⁵⁺ is V, Nb, Ta, or Sb,(4) having the valence A²⁺(B²⁺ _(0.33)B⁵⁺ _(0.67))O₃, wherein A²⁺ is Ca,Sr, or Ba, B²⁺ is Mg, Ca, Cd, Ni, or Zn, B⁵⁺ is Nb, Ta, or Sb, (5)having the valence A²⁺(B²⁺ _(0.5)B⁶⁺ _(0.5))O₃, wherein A²⁺ is Ca, Sr,or Ba, B²⁺ is Mg, Ca, Sr, Ba, Cd, Ni, or Zn, B⁶⁺ is Mo, W or Re, (6)having the valence A³⁺ _(0.33)B⁵⁺O₃, wherein A³⁺ is Y, La, Ce, Pr, Nd,Sm, Gd, Dy, Ho, or Er, B⁵⁺ is Nb or Ta, or (7) having the valenceA³⁺(B²⁺ _(0.5)B⁴⁺ _(0.5))O₃, where A³⁺ is La or a lanthanide, B²⁺is Mg,and B⁴⁺ is Ti, interleaved Bi₂O₂, or a perovskite-like structure, iii)(1) fluorite or distorted fluorite of A_(1−x−y)B_(x)C_(y)O_(2+/−z),where A is Zr, Hf, or Ce, B is Mg, Ca, Y, Sc, or a rare earth, C is V,Nb, or Ta, where x<1, y<1, x+y<1, and z depends upon the valence of Band C, wherein, if B is 2+, then z=2+0.5y−x, and if B is 3+, thenz=2+0.5y−0.5x, (2) a fluorite like compound ofA_(1−x−y)B_(x)C_(y)O_(2+/−z), where A is Zr, Hf, or Ce, B is Mg or Ca,and C is W or Mo, where x<1, y<1 and x+y<1, and z is 2+y−x, (3) asheelite type structure of ABO₄, where A is Mg or Ca and B is W or Mo,(4) a fergusonite type structure of M^(III)NbO₄, M^(III)TaO₄ orM^(III)VO₄, where M^(III) is a metal of valence +3, or formula ABO₄where A is Y or a rare earth and B is Nb, Ta or V, (5) an aniondefective fluorite, or (6) a fluorite related ABO₄ compound, withvalence A²⁺B⁶⁺O₃ or A³⁺B⁵⁺O₃, wherein A²⁺ is Ca or Ba, B⁶⁺ is Cr, A³⁺ isCr, and B⁵⁺ is Nb, iv) ilmenite of formula ABO₃, wherein A is Ni, Co, Mnor Fe and B is Ti, or giekielite where A is Mg and B is Ti, v)pseudobrookite crystal structure of the formula A₂BO₅, where A is Al orFe and B is Ti, vi) a tetragonal bronze structure based on ReO₃-likeblocks or a Nb₂O₅—WO₃ mixture, vii) a tetragonal bronze of valenceA²⁺B⁵⁺ ₂O₆, wherein A²⁺ is Sr or Ba and B⁵⁺ is Nb or Ta, or thesuperstructure A²⁺ ₅B⁵⁺ ₁₀O₃₀, A²⁺ ₆B⁴⁺ ₂B⁵⁺ ₈O₃₀, or A²⁺ ₅B³⁺B⁴⁺ ₃B⁵⁺₇O₃₀, where A²⁺ is Ca, Sr, or Ba, B³⁺ is La or a lanthanide, B⁴⁺is Ti,and B⁵⁺ is Nb or Ta, viii) rutile structure of AO₂, wherein A is Ti, Sn,or Mn, ix) a trirutile crystal structure of AB₂O₆, where A is Mg, Cr, orV and B is Ta, W, or Sb; or CaTa₂O₆, or x) a cubic rare earth (C-M₂O₃)structure A₂O₃, where A is Y or a rare earth, or a mixture thereof or asolid solution thereof.
 27. The solid oxide fuel cell of claim 23,wherein the insulating oxide ceramic comprises one or more of i)pyrochlore or distorted pyrochlore crystal structure of La₂Zr₂O₇,Y₂Zr₂O₇, Nd₂a₂O₇, Gd₂a₂O₇, Er₂a₂O₇, La₂Hf₂O₇, Y₂W₂O₇, Nd₂Hf₂O₇,Gd₂Sn₂O₇, Er₂Hf₂O₇, La₂Sn₂O₇, Y₂Sn₂O₇, Nd₂Sn₂O₇, Gd₂Sn₂O₇, or Er₂Sn₂O₇,ii) perovskite, distorted perovskite crystal structure, superstructureof perovskite, or interleaved perovskite-like structure of SrZrO₃,BaZrO₃, SrHfO₃, BaHfO₃, SrSnO₃, BaSnO₃, BaTiO₃, or SrTiO₃, iii)fluorite; distorted fluorite of A_(1−x−y)B_(x)C_(y)O_(2+/−z), where A isZr, Hf, or Ce and B is Mg, Ca, Y, Sc, or a rare earth and C is V, Nb, orTa where x<1, y<1, x+y<1, y/x>0.5 and z depends upon the valence of Band C, wherein, if B is 2+, then z=2+0.5y−x, and if B is 3+, thenz=2+0.5y−0.5x; fluorite like compound of A_(1−x−y)B_(x)C_(y)O_(2+/−z),where A is Zr, Hf, or Ce, B is Mg or Ca and C is W or Mo, where x<1,y<1, x+y<1, y/x>0.5, and, and z is 2+y−x; sheelite type structure ofABO₄, where A is Mg or Ca, B is W or Mo; fergusonite type structure ofM^(III)NbO₄, M^(III)TaO₄, or M^(III)VO₄; or formula ABO₄ where A is Y ora rare earth and B is Nb, Ta or V, or iv) rutile AO₂ structure, whereinA is Ti or Sn, or a mixture thereof or a solid solution thereof.
 28. Thesolid oxide fuel cell of claim 23, wherein insulating oxide ceramic isnot yttria stabilized zirconia or lanthanium zirconate.
 29. The solidoxide fuel cell of claim 23, wherein the one or more insulating oxideceramics has the following crystal structure class, super class,derivative structure or superstructure of the following crystalstructure types: i) perovskite, distorted perovskite, superstructure ofperovskite, or interleaved perovskite-like structure, ii) fluorite,distorted fluorite, fluorite like, anion defective fluorite, sheelite,fergusonite, or a fluorite related ABO₄ compound, iii) ilmenite, iv)pseudobrookite A₂BO₅, v) stoichiometric structure based on ReO₃-likeblocks, vi) bronze or tetragonal bronze structure based on ReO₃-likeblocks, vii) rutile, viii) trirutile crystal structure or columbitecrystal structure of AB₂O₆, or ix) cubic rare earth (C-M₂O₃) structure,or a mixture thereof or a solid solution thereof.
 30. The solid oxidefuel cell of claim 23, wherein the electrolyte is disposed between theanode and the cathode, the anode of one fuel cell is electricallyconnected to the cathode of another fuel cell by a via pad at the anodeand a via pad at the cathode, the via pads are electrically connected toeach other with a via fill that traverses through the electrolyte, thebus bar is electrically connected to the electrode at each end of theelectrolyte, and the seal is disposed between the electrolyte and aframe adjoining the seal.